Hydraulic tracing mechanism



W. I. EVANS Aug. 17, 1954 HYDRAULIC TRACING MECHANISM 3 Shee'Fs-Sheet 1 Filed latch 23, 1951 Fig.3

INVHV TOR. WfT/VDELL E VANS 2 xemdzm 14 T TURN/5Y8.

1954 w. l. EVANS 2,686,650

HYDRAULIC TRACING MECHANISM Filed March 23, 1951 3 Sheets-Sheet 2 INVENTOR. Wf/VDELL EVANS BY [Q mafmmnyw Aug. 17, 1954 w. l. EVANS 2,686,650

HYDRAULIC 'IYRACING MECHANISM Filed March 23, 1951 s Sheets-Sheet 3 Fig. '7

INVENTOR. WENDELL EVANS hmmuM Patented Aug. 17, 1954 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to pattern controlled reproducing machines and has particular reference to an improved hydraulic operating mechanism for such machines.

One of the principal objects of the present invention is the provision of an improved pattern actuable control mechanism for automatic determination of the relative rates of movement of a pair of machine tool slides for determining the resultant contour path followed by a reproducing tool.

A further object of the invention is the provision of an improved automatic control mechanism for contouring machines for eiiecting an improved sensitivity in determintion of the relationship between the relative slide movements irrespective of the feed rates being employed for the particular contouring operation which will be particularly effective in maintaining a substantially constant cutting rate irrespective of the directional path and prevent possible rate fluctuations in the movement of individual slides due to unequal resistance to movement as respects the parts being actuated.

An additional object of the present invention is the provision of a tracer actuable control valve mechanism embodying variable resistance means capableof utilization, not only to determine the selective or proportional distribution of hydraulic actuating medium to a plurality of members but which. has the additional capacity of adjustment to vary the rate of .power transmittal effected by corresponding movements of thecontrol valve mechanism.

Other objects andadvantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that anymodifications may be made in the exact structural details there shown and described, within thescope of the appended claims, without departing fromor exceeding the spirit of the invention. Figure 1 is a plan view of a lathe structure embodying the present invention.

Figure 2 is a diagrammaticvertical sectional view on the line 2-4 of Figure 1.

Figure 3 is a sectional view on the line 3-3 of Figure 2. i

' Figure 4 is a vertical section of the tracer body on line 4-4 of Figure 2.

Figure 5 is a vertical section on the line 5-5 of Figure 2.

Figurefi is a fragmentary perspective view: of aportion of the tracervvalve mechanism.

Figure 7 is a view in elevation of thetracer valve and bushing with the tracer housing shown in section, and

Figure 8 is a longitudinal sectional view of the tracer bushing with sliding valve removed.

In the drawings, the numeral l 0 designates the bed of a lathe, supporting the headstock i3 and tailstock l4 between which are mounted the work piece 55, and having ways i l for the longitudinally movable tool carriage l2. Transversely movable on the carriage I2 is a cross slide [6 provided with a toolhead ll suitably supporting tool It for operation on the work piece i5. An adjusting screw It is provided intervening the cross slide and the toolhead I! for effecting feeding or other adjusting movement of the tool with respect to the work. For effectinglongitudinal movement of the carriage, the bed is provided with a rack 26 engaged by pinion Zl actuable by the reversible hydraulic motor 22 secured to the underside of the carriage.

Mounted on the carriage i2 is a hydraulic cylinder 23 containing a piston 24 provided with piston rod 25 secured to the slide I 6. This structure provides a differentialarea piston structure in that the rod side of the piston possesses a smaller efiective area than the free or opposite side of the piston. Consequently, a lesser pressure reactingonthe large end of the :piston will overcome a higher unit pressure reacting on the rod side or face of the piston, a feature which is advan tageously utilized in connection with the specific form of invention here shown.

The bed ill of the lathe is provided with rearwardly extending brackets 26 adjustably support ing a pattern member 21 for engagement with the tracer finger contact such asthe roller 28 carried by the sliding tracer finger 29 mounted in extension 30 of the tracer bodyor housing 3 I. This housing is suitably mounted on the cross slide [6 in any conventional manner, the attachment hereshown comprising a bolt 32.

Disposed withinthe tracer body3l is: a valve bushing designated as an entirety by the numeral 33 having a bore 34 to receive the slidable tracer valve 35. Peripherally, the bushing has a fluid tight fit with the interior of the housing and is held against rotation with respect thereto by pin 36. The bushing is turned or reduced in diameter as at the points 31, 38, and 39 and, additionally, transversely slotted to produce the diametrically oppositepairs of fingers or webs 40, 4t, and}? intervening the full diameter portions 43, 44,45,

and 4a of the bushing. :The structure thus de-f scribed therefore provides acomplete circumscrib ing guide for the sliding valve 35 but interrupted at the areas 37, 38, and 39, the upper and lower interrupted areas being placed in communication with each other as by the arcuate grooves or spaces 41 intervening the reduced portions 35, 4|, and 42 of the bushing and the interior of the tracer body 3|. If additional space is desired for free annular flow of the hydraulic medium within the valve passages, supplemental aligned grooves 48, 49, and 50 may be formed in the inner face of the tracer body as shown in Figure 2.

The specific structure of the tracer valve 35 is particularly illustrated in Figures 2 and 6. By reference to these figures, it will be seen that the valve is provided at one end with a terminal head engaging the contact 52 on the inner end of the sliding tracer finger 29, being urged outwardly in the housing 3| and against said finger by spring 53 interposed between the head 5! and the shoulder 54 of the bushing 33. The valve is further formed with the cylindrical portions 54', 55, and 55 separated by the reduced portions 51 and 58 which when the valve is in position within the bushing are substantially aligned with the portions 45 and 44 of the bushing.

It will be noted that the inner or right hand shoulder of the portion 56 as shown in Figures 2 and 4 has a pair of relieved or recessed portions formed by the beveled or tapered segmental faces 59 which, when the valve is in the intermediate or neutral position shown in Figure 2, form outwardly tapering throats or throttle portions providing passages intervening the area around the reduced portion 58 of the valve and'the circumferential space 3L'permitting flow by way of this passage and space 31 to conduit 65, leading to the motor 22. Similarly, the cylindrical portion 55, as at one side adjacent the reduced portion 58, the segmental beveled areas 5| and at its opposite face similar segmental beveled areas 52 disposed in cooperative relation respectively with the edges or shoulders bounding the adjacent bushing portions 44 and Y45, while the portion 54' isprovided with the segmental beveled'faces 63 disposed in opposition to the opposite or forward shouldered face of the bushing portion 45.

The tracer finger 29 is supported for free'axial or longitudinal movement in the forward portion of the tracer housing by the balls or-antifriction members 64' but is held against rotative movement by the :pin or key 65 to preserve proper to. denote the rotational adjusted position of the knob and thus of the'valve. A pointer .or

index finger H carried by the extension of the tracer head or housing in whichshaft 63 is rotatably mounted, for other. suitably designating means, cooperates with the index indicia for determination of the amount of 'rotative adjust- V ment imparted to the valve 35.

,Itwill be evidentpthat if the several tapered segmental'portions of the valve stem are positioned to lie completely within the slotted portions ofzthe bushing and between the Webs or fingers 4|, there willbeminimum restriction as respects fluid flow within the tracer valve structureh However, 'as the valve 35 is rotatably adjusted to a midposition, for-example, as illus trated in Figure 5, a portion of the severaltaperedw 4 portions will lie within and be blanked off by the portions 4 I, thus throttling or reducing the potential flow by way of the said tapered portions.

For effecting hydraulic operation of the piston and cylinder motormechanism 23-44 for positioning of cross slide l5 and the actuation of the reversible hydraulic motor 22, there is provided a tank or sump 12 containing suitable hydraulic actuating medium which is drawn from the tank by pump 13 for discharge into the pressure line 14. Excess of fluid over the operating requirementsis returned from the pressure side of the pump through variable relief valve 15 to the sump. Pressure line 14 has a branch 16 directly connected to the piston rod end of cylinder 23, continuously reacting when the pump is in operation to urge the tool slide it in a direction toward the work piece iii. The main line 14 terminates at the port area 38 between the portions 44 and 45 of the tracer valve bushing, thus introducing pressure into this general area so that in the neutral position of the tracer valve shown, a portion of the introduced pressure will flow by way of 6| around reduced valve portion 58 and V spool relief 59 through conduit 55 to operate the motor 22 while at the same time the intermediate rib l7 acts as a flow divider so that a portion of the available fluid may pass by way of 52, the

. space surrounding 5?, port 73 and conduit 19 to the larger piston area or right hand end of cylinder 23, building, up a pressure adequate to counterbalance the existing smaller area or piston rod end of the cylinder so that the carriage H5 is held in a stationary position. This pressure balancing ismade possible by the fact that a portion of the pressure fluid or a partial relief condition is effected by way of the taper valve portion 53 through the area 38 and reservoir conduit 80; In other words, when the tracer finger is deflected or moved either to the left or the right from the effective neutral, an unbalanced pressure conditionds created within the cylinder 23 causing a follow-up readjustment of theislide it until a hydraulically effective neutral is automatically established. It

a will be'evident to those conversant with the art of hydraulic tracing that any such displacement of tracer valve 35 by finger 23, normally quite minute in amount, while determining the forward or back movement of the slide it will at the same time move either the taper throttle 6| toward the shoulder of valve bushing 44 or alternatively the taper portion53 toward the opposite porting edge of 44, in either event restricting the circuit flow from it to 50 and slowing down or stopping the traverse movement during the accelerated in or out movement of the tool and tool slide.

During such sliding movement of the valve, gear 55 will move axially with the valve and relative to gear 51, the amount of possible movement,

however, being insufficient to move these gears out'of mesh one with the other, and as there is pressure in the 1 maximum rate of operation of one of thedirectional control motors and a second independent throttle means for determining the maximum potential rate of actuation of the motive means for effecting. an angularly related directional movementof th machine parts. Additionally, attention is invited to the fact that whereas known prior art structures having tracer valve mechanisms constructed to take care of a certain maximumrate of flow to one or the other of the controlledqpartswere subject to certain operational difliculties and inaccuracies in control when reduction was made-in the amount of availableactuating fiuid by decrease in its potential rate of supply, that, the present invention involves no decreasein th rate of supply or availability of volume of actuating fluid, but independently throttles 1 and controls separately the amount available to the individual motor control valve systems, thus insuring thecorrect controlled functioning of each of said motors for both fast and slow feed rate operations.

It is wellunderstood in connection with tracer valve mechanisms that the matter of neutral, maximum opening, and intermediate relationships of the control elements of tracing valve mechanisms are determined primarily by the hydraulic reaction through the valve mechanisms rather than by strict consideration of physical relationship of the parts, and that such valves are so constructed that a thousandth of an inch or less of .axial movement-of a tracer valve will cause appreciable variation in the flow and pressure. effects of the hydraulic system controlled thereby. I It will, therefore, be understood that the principles of the present invention and the physical relationship of the parts have of necessity been diagrammatically exaggeratedfor clarity of understandingbut that the clearances in actual use will ordinarily be much less than those physically-indicated in the drawings. Attention, however, is invited to the fact that the taper angle of the control portions 62 and B3 in the form illustratedis of the nature of aboutl30 degrees while thetaper angle of the faces 59 and El have been shown with a steeper taper in the nature of 50 degrees: In practice, valves of the present invention are constructed as indicated and described so that when thetracer valve35 is in its hydraulic neutral position as respects in and out or cross feed movement or the tool:slide or rotatively adjusted to effect maximum delivery by way of the valve portions 59 andBI that a maximumtraverse or feed rateactuation of the motor 22 will be effected.

This relationship having been determined, 62

and 63 can then be changed or modified to the extent desired, as by varying their angularity, so that when 59 or 6|, depending on the direction of axial movement of the valve 35, blocks off or stops flow to motor 22 and the feed of the carriage; these portions will pass enough fluid into or permitits exhaust from the large end of cylinder 23 so thatthe cross slide It will move atits maximumrateg This rate is preferably, although not necessarily, equivalent to the selected maximum longitudinal rate of movementof the carriage. These maximum potential rates having been determined by vproper formation or adjustment of therelationship of the valveconfigurations, therespective rates: can then ,be correspondingly reduced byrotation'ofmemberfi which serves to throttle 'downrcorrespondingly the respective flows, thus determining theparticularrrate to beutilized for longitudinal :teed: ;and,afor-1cross movement or the rate in anyparticular contouring or angula'rly re'- lated direction of movement of tool and work resultant from combined utilization of the two flows. Due, however, tothe provision of the rate control means within the tracer valve and indi vidual to the respective motors as distinguished from employment of arate control valve in the input line determining the general flow only to the tracer mechanism, there is no drop in pressure at the shoulder 17 effective as respects the flow dividing faces 61 and B2, and, therefore, no loss of tracer valve sensitivity or accuracyof control attendant upon appreciable reduction in feed rates employe From the foregoing description it will be evidentthat the spaces 48, 49, and 50 in communication with and forming continuations of the respective conduits til, 14, and 86 form the terminal ports for these conduits, each of which ports is individually boundediby a pair of walls formed by radial planes intersecting the axis of the valve and the bore in which the valve slides to provide the arcuate or peripheral edges or shoulders bounding the bore for cooperation as respects each port with the shoulders on the valve membei'.

It will also be evident that the, major measurement of each of the spools on the valve member is such as to physically overlap its associated port but that the double taper on the central or inter mediate valve spool, as respects the relieved orrecessed portion of this valve spool and the relieved or tapered portions of the other spools facing the intermediate spool provide arcuate or peripheral shoulders on the valve spools which cooperate with the shouldersor" the port areas. It will further be evident that these valve shoulders, whether of physically overlap or underlap characteristio, are so arranged as to have a hydraulic, underlap so that there may be flow from one port to another by way of the recessed or reduced intermediate portions of the valve while the coop,- erative relation of these annular or peripheral shoulders provide variable hydraulic resistances depending upon axial movement of the valve to control the proportioning of the how from the port area 49 to the port areas 48 and 5b. Also, it Will be evident that the central or intermediate spool 55 is positionable either to divide the now or completely to shut off the flow in one direction or the other, while the end spools 5t and 56 in this respect are equally inversely effective to providea resistance cutting down or shutting ofi flow into the port areas 50 and 48. At the same time the bounding shoulders of the several relieved portions on the valve member 35, such as 8l82--83 t4, which are disposed in axial planes cooperative with the axial plane bounding shoulders 855-436-431 of the webs 404l-42 variably limit or restrict the effective pressure or fluid transmitting areas or resistancesunder control of the first set of shoulders, dependent upon the relative rotative adjustment of the valve 35 and its support. This latter variation is, of course, dependent upon the particular positional relationship of the various relieved portions such as 59 of the valve spools as respects the positional location of the corresponding axial web shoulders. Consequently, different relationships may be established and difierent types of variationef fected upon rotation of the valve, dependent upon such structural relationships, although in the, present instance the parts have been'shown so, dimensionally constructed and arranged that axial movement produces inverse variations in. resistance efiects as respects adjacent :arcuatel 7 port shoulders, while 'rotative' adjustment effects corresponding modifications or throttling's of the eflective resistance areas.

1 It will be understood that while for simplicity of manufacture and assembly'the tracer body or housing has been shown as a two-part member embodying the outer shell or housing 3| with a contained bushing 33, the parts being'tightly fitted and'pinned together, that when so assembledthese constitute a unitary or one piece structure,*the prime essence of the invention therefore being the configuration and relationship between the outer member having the described shoulders and ports and the sliding inner member or valve with'its cooperating configurations.

.The tracer valvestructure shown in Figure 2 is indicated in what may be termed itsstatic position, that is; a position'in which balanced pressure conditions lock the piston 2:3 and thus the tool slide l6 against in and out movement, and: the entire flow of motion producing fluid is to the motor- 22 to effect traverse of the carriage. This is the condition existing when the movable valve-member is held by the tracer finger in its neutralpositionas when following a straight or plane surface. In the relationship here illustrated it will be noted that the inner valve member is provided with the grooved or relieved portionship'the relative rotation of the inner and outer valve elements serves to vary the effective area ofthe resistances and thus the static flow conditions in the'absence of tracer finger controlled relative movement of the parts'in an axial direction and establish the maximum flow avail V able.

'Additionally,'however, when the valve is in tion will vary the volumetric flow past the shoul ders for any relative axial positioning. 7 i -2. A tracer valve structureincluding a sup porting housing having a central-bore formed with a plurality of internal grooves providing axially spaced annular areas circumscribing-tl'ie bore and radially extending surfaces bounding said areas to provide throttling shoulders,;said bore having additional axially extending portions intervening said surfaces to provide additionalthrottling shoulders, and a control valve slidably mounted within the bore, said'control valve having a fiowdividing portion positionable intermediate a pair of said radially extending bounding surfaces having segmental lateral shoulders disposable in cooperative relation with the radially extending surfaces and axially extending shoulder portions for cooperation with a live Qor dynamic condition caused by tracer variance in the position of the parts, the arcuate cooperating shoulders in their varying positional arrangements as effected by deviations of the controlling pattern from a straight line traverse path; cause automatic variationsinthe dynamic new resistances'for determination of the relationshipoof' the, carriage and slide movements. What is claimed is: V .1. A tracer valve structure including a sup- ,-porting housing having a central bore formed with a plurality of internal grooves providingaxtional throttling shoulders, and a control valve 7 slidably mounted within the bore,,said;controlj V valve having a flow dividing portion positionable intermediate a pair ofsaid radially'extending bounding surfaces having segmental lateral shoulders disposable in cooperative relation with the radially extending surfaces and axially-extending shoulder portions forcooperation with the axially extending throttling shoulders of the bore, whereby relative axial movement; of, the housing andvalve will vary the proportional flow byaway ofrthe radial shoulders and relative rotafinger determined relative axial adjustment or the axially extending throttling shoulders of the bore, whereby relative axial movement of the housing and valve will vary the proportional flow by way of the radial shoulders and relative rotationwill vary the volumetric flow past the shoulders for any relative axial positioning, the-supporting housing having additionalsimilarly ar ranged shouldered portions axially spaced from the first set of shoulders and the valve having additional axially spaced corresponding shoulders for cooperation with the additional shoulders of the supporting housing and connected with the first shouldered portion of the valve by reduced portions providing circumscribing passages, the additional radially'shouldered portions of the valve being disposed in opposed relation to the adjacent central radial shoulders'of the valve and the axially extending shoulders being: disposed in corresponding relation to the axially disposed shoulders on the central portion of thevalve' whereby relative axial movement of the housing and valve will inversely vary the resistance effects of the opposed radial sets of shoulders while rotation of the valve will corre: spondingly varythe resistance efiect s of the axially extending shoulder portions of the valve.' Q

3. A tracer valve structure including a support ing housing having a central bore for'medwith a 'plurality of internal grooves providingPaxially spaced annular areas circumscribingthe bore and radially extending surfaces bounding said areas tioningthesupportinghousing having additionalsimilarly arranged shouldredportions axiallyspaced; from; the Ifirst set of shoulders; and the;

.valve having additional axiall y spaced corre to provide throttling shoulders,said borehaving additional axially extending portions intervening said surfaces to provide additional throttling shoulders, a'ccntrol valve slidably'mounted' with in the bore, said control valve havinga fiowdividing portion positionable intermediate a ,pair of said radiallyextending bounding surfaces have 7 ing segmental lateral shoulders 6.1519053131811100? operative relation with the radially extending surfaces and? axially extending shoulderportions for cooperationivith the axially extending throtr tling shoulders of the borejwherebyrelative axial movement of the housing and valve willivary the proportional new by ,way' of the radial shoulders; '7

and relative rotation will vary the volumetric flow past the shoulders forany relative axial: posisponding shoulders for cooperationyivith the ad'- ditionalshoulders of the supporting housingeand connected withthefirst shoulderedfportien'ofthei V valve by reduced portions providingw circumscribeins-1 passages, the additional radially "shouldered portions, of-the valve beingl'disposed in opposed relation to the adjacent central radial shoulders of the valve and the axially extending shoulders being disposed in corresponding. relation to the axially disposed shoulders on the central portion of the valve whereby relative axial movement of the housing and valve will inversely vary the resistance effects of the opposed: radial sets of shoulders while rotation of the valve will correspondingly vary the resistance efiects of the axially extending shoulder portions of the valve, means for effecting a resilient axial urge of the Valve in one direction, and a tracer actuable finger slidable within the supporting housing and opposing the resilient actuation of the valve to dictate the axial position thereof.

4. A tracer valve structure including a supporting housing having a central bore formed with a plurality of internal grooves providing axially spaced annular areas circumscribing the bore and radially extending surfaces bounding said areas to provide throttling shoulders, said bore having additional axially extending portions intervening said surfaces to provide additional throttling shoulders, a control valve slidably mounted within the bore, said control valve having a flow dividing portion positionable intermediate a pair of said radially extending bounding surfaces having segmental lateral shoulders disposable in cooperative relation with the radially extending surfaces and axially extending shoulder portions for cooperation with the axially extending throttling shoulders of the bore, whereby relative axial movement of the housing and valve will vary the proportional flow by way of the radial shoulders and relative rotation will vary the volumetric flow past the shoulders for any relative axial positioning, the supporting housing having additional similarly arranged shouldered portions axially spaced from the first set of shoulders and the valve having additional axially spaced corresponding shoulders for cooperation With the additional shoulders of the supporting housing and connected with the first shouldered portion of the valve by reduced portions providing circumscribing passages, the additional radially shouldered portions of the valve being disposed in opposed relation to the adjacent central radial shoulders of the valve and the axially extending shoulders being disposed in corresponding relation to the axially disposed shoulders on the central portion of the valve whereby relative axial movement of the housing and valve will inversely vary the resistance effects of the opposed radial sets of shoulders while rotation of the valve will correspondingly vary the resistance effects of the axially extending shoulder portions of the valve, means for effecting a resilient axial urge of the valve in one direction, a tracer actuable finger slidable within the supporting housing and opposing the resilient actuation of the valve to dictate the axial position thereof, a rotary adjuster for the valve carried by the housing, and a positive drive axially sliding connection between the adjuster and the valve for effecting rotary adjustment of the valve while permitting independent axial movement thereof.

5. A tracer valve structure including a supporting housing, a valve bushing contained within the housing having a central bore and having formed therein a plurality of transverse axially spaced slots providing segmental spaces each bounded by a first set of shoulders, each formed by the intersection of a plane normal to its axis with the bushing and a second series of shouliii) 10 ders formed by the intersection of a plane paral lel with its axis with the bushing, input and output distribution conduits communicating with respective slotted areas of the bushing, and a control valve member slidable and rotatably mounted within thebushing and formed with a plurality of axially spaced segmental tapered portions providing as to each segment a peripheral shoulder for cooperation with one of the radial plane shoulders of the slotted bushing and additional bounding end shoulders for cooperation with the axial plane shoulders of thebushing, the spacing between the peripheral shoulders on the valve being-greater than the spacing between adjacent radial plane shoulders of the bushing and the tapers of the tapered portions extending in the direction of the cooperating shoulders on the bushing, a tracer finger carried by the housing and disposed in cooperative engagement with the valve for dictating the axial positioning thereof to vary the relationship between the radial plane shoulders and the valve to vary the resistance effecting spacing of said shoulders, and additional means for rotating the valve to vary the relationship between the axial. plane shoulders of the valve and the bushing to vars the effective arcuate length of the radial plane shoulders.

6. A tracer control valve structure for machine tools or the like including a supporting housing, bushing means within the housing having a central tracer valve receiving bore and a plurality of axially spaced internal annular spaces communicating with the bore. connected by intermediate shouldered portions, the bushing having arcuate shoulder portions bounding the annular areas, and a tracer valve mounted in the bore of the bushing for rotativeand axial sliding movements relative thereto, said valve having central and terminal spool portions spaced in correspondence with the spacing intervening the annular areas of the bushing and reduced passage providing portions intervening said spools, the central of said spools having segmental relieved portions on both faces thereof providing circumferentially disposed shoulders for cooperation with the internal shoulders of the bushing adjacent the annular recesses and having additional axially extending shoulders for cooperation with the axially extending shoulders on the connecting portions of the bushing intermediate said spaces, and the terminal spools of the valve having corresponding segmental relieved portions providing peripheral shoulders for cooperation with spaced annular shoulders of the bushing and axially extending shoulders for cooperation with the axially extending shoulders of the connecting portions of the bushing, means for rotating the valve with respect to the bushing to vary the length of effective resistance area between the axially extending shoulders of the bushing and valve, and additional means for axially relatively shifting the bushing and valve inversely to vary the resistance effects of the respective cooperating peripheral shoulders of the valve spools and the bushing.

'7. A hydraulic tracer control mechanism for machine tools, said control mechanism including a tracer housing having a pressure inlet port, a first axially spaced outlet port, a second outlet port, and a third outlet port axially remote as respects the inlet and second outlet port, said ports having bounding faces providing resistance shoulders, the housing member having a, central bore intersecting said shoulders, and a control valve mounted within said bore having a central spool'portion overlying the inlet port, and terminal spool portions overlying the remote outlet ports,'the spool overlying'the inlet port havingarcuate relieved portions on its opposite faces providing hydraulically underlapped shoulders positionable intermediate the bounding shoulders of the inlet port, and the other spools each having an arcuate relieved portion opposing the central spool and providing a resistance shoulder for cooperation with an outlet port shoulder, the spacings between the opposing spool shoulders beinggreater than the spacing between their confronting port shoulders whereby relative shifting of the spools and ports will increase the hydraulic resistance effect between one set of the shoulders while decreasing said effect as respects the confronting set of shoulders, radially extending bounding shoulders determining the arcuate extent of the ports, shoulders on the spools bounding the arcuate relieved portions of the spools, and means to effect relative adjustment of the last-mentioned shoulders of the ports and spools to varythe arcuately' effective length of the relieved portions of the spools.

8. A hydraulic tracer control mechanism for machine tools, said control mechanism including a tracer housing having a pressure inlet port, a first axially spaced outlet port, a second outlet port, and a third outlet port axially remote as respects the inlet and second outlet port, said ports having bounding faces providing resistance shoulders, the housing member having a central bore intersecting said shoulders, and a control valve mounted within said bore having a central spool portion overlying the inlet port and terminal spool portions overlying the remote outlet ports, the spool overlying the inlet port having arcuate relieved portions on its opposite faces providing hydraulically underlapped. shoulders positionable intermediate the bounding shoulders of the inlet port, and the other spools each having an arcuate relievedportion opposing the central spool and providing a resistance shoulder for cooperation with an outlet port shoulder, the spacings between the opposing spool shoulders being greater than the spacing between their con-fronting port shoulders: whereby relative shiftingof the spools and ports will increase the hydraulic resistance effectv bee tween one set of the shoulders while decreasing said effect as respects the confronting set off shoulders, radially extending bounding shoulders determining the arcuate extent of the ports, shoulders on the spools bounding the arcuate relieved portions of the spools, and means to effect relative adjustment of the last-mentioned shoulders of the ports and spools to vary the arcuately effective length of the releived portions of the spools, the valve portions intermediate. the spools having reduced areas providing passages interconnecting the respective opposed relieved faces of the spools.

9., A tracer valve mechanism for control oi the relative movements of a plurality of reproducing machine tool slides, said valve mechanism including a pair of telescoping valve elements, ,a pattern actuable tracer finger carried by one of said valve elements and movable relative thereto for reaction on the other'of said valve elements to control the relative positions of the valve elements, one of said valve elements having formed therein an inlet port and pres,- sure inlet areas and spaced outlet, ports and pressure outlet areas, and the pair of valve elements having relieved portions with bounding shoulders forming resistance areas, said relieved portions and resistance areas providing tortuous passages from in et, to outlet ports by way of the shoulders and relieved portions, whereby relative tracer finger determined adjustment of the parts will vary the resistance effects of the. areas between said shoulders, and means to vary the extent of such areas available for tracer controlled flow within the valve.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 685,510 Flint Oct. 29, 1901 1,959,178 Sassen May 15, 1934 1,962,851 Wilson July 24, 1934 2,003,292 Holzwartz June 4, 1935 2,025,148 Howe Dec. 31, 1935 2,059,363 Kimball Nov. 3, 1936 2,141,428 Carroll Dec. 27', 1938 2,314,841 Crafts Mar. 23', 1.9.43 2,332,533 Roehm Oct. 26, 1943 2,386,825 Turchan et. al Oct. 16; 1945- 2,39'1,492 Tiirchan et a1. Dec. 25 1945 2,412,549 Yates et al Dec. 10, 1946 2,562,284 Tancred July 31, 1951 

